The known materials for the manufacture of litter for animals are essentially natural products of mineral origin such as pumice stone, bentonite, clay minerals, for example sepiolite, diatomite, or of organic origin such as wood flour, sawdust and peat which, because of their porous structure, have the property of absorbing liquids in their pores.
For years granulated drying and/or absorbing agents have been used for keeping household pets clean, especially in densely populated urban and suburban areas. Such products are mostly bought and used in large quantities by owners of small animals, in particular cats.
Nowadays a variety of products with very different properties is marketed under the name "cat litter". The majority of these products, as already mentioned above, are manufactured on a mineral basis.
An animal litter of this kind is known, for example, from DE-PS 31 21 403, which is made using a porous inorganic material with a pore structure. The porous material used here consists of calcium silicate granules and/or calcium silicate powder which has a pH-value between about 5.8 and 6.2. The known animal litter made from calcium silicate granules having a pore radius of less than 500 nm retains its shape and consistency and is bactericidal. However, after prolonged use of such materials an unpleasant smell develops so that the animal litter often has to be changed even though the absorbing capacity is by no means exhausted.
The afore-mentioned animal litter products with their different characteristics do, however, have further disadvantages. Their high specific gravity causes great practical problems in the supply and transportation of the packaged product Some of the animal litter preparations consist of sharp-edged--in particular broken--stones, which leads animals with paws to avoid the sharp granules.
DE-OS 36 44 826 describes an animal litter that consists of a mixture of filler materials, gypsum and catalysts, the materials being mixed when they are dry and compressed under high pressure. The process of forming by pressing in dies does, however, have many disadvantages, e.g. high consumption of energy, significant wear and high product density.
In relation to the weight of the product the take-up of liquid in many known products is very small. After reaching their absorptive capacity these products tend to swell and thus form clumps. This effect is still more marked in the case of diatomite, which becomes very sticky, greasy and even pasty. These disadvantageous properties necessarily lead to difficulties in handling such products. Because of these product characteristics the litter must also be changed often and as a result more is used.
In the manufacture of these animal litter materials a large proportion of fine dust is formed as a result of the way they are crushed, and by abrasion in the drums or other containers during storage, transport and handling between the manufacturer and consumer. Handling the open container in the pet owner's home raises a great deal of dust, especially when changing the litter in the boxes. In addition this high proportion of fine dust is bad for the animals, since they inhale the dust when scratching in such products.
After use, such water-insoluble stone and/or mineral animal litter products can only be disposed of as or with domestic waste. This causes the waste disposal plants to be burdened with a not insignificant amount of such waste products. In Switzerland and in the Federal Republic of Germany, for example, about 40,000 tons and 500,000 tons respectively of waste consisting of this kind of product accumulates each year. This shows that the market for such (albeit improved) animal litter products is very large, especially in densely populated urban and suburban areas.